CHICAGO (Reuters life!) - Being overweight may not kill you, but it could lead to obesity, U.S. health experts cautioned on Wednesday in response to research suggesting that being a bit heavy does not raise the risk of death.

A study published in the Journal of the American Medical Association found that being overweight did not increase the risk of dying from heart disease and cancer.

It also was linked with a significantly decreased rate of death from non-cancer and non-heart related causes, such as accidents or diseases like Alzheimer's.

Experts noted that the research only looked at death rates, not overall health. It did find that obesity was associated with a significantly higher risk of death from heart disease.

"You should not take heart in the idea that if you are only overweight you are OK," said Dr. Robert Kushner, a professor of Medicine at Northwestern University who specializes in nutrition and diet.

"Given time, there is a high likelihood you will be obese because people gain weight as they age in this country," Kushner said in a telephone interview.

He said many studies have shown that as one starts gaining weight, health risks develop. "We've done very well at medicating people to keep the medical complications at bay, which allows people to live longer," he said.

The study, conducted by Katherine Flegal of the U.S. Centers for Disease Control and Prevention, looked at specific causes of deaths in relation to body mass index, a ratio of height and weight.

A BMI of 25 to less than 30 is considered overweight, while a BMI of 30 or greater is considered obese.

The researchers found that people in the overweight category were no more likely than healthy-weight people to develop heart disease or cancer and had far fewer deaths from other causes, such as accidents or diseases such as Parkinson's or Alzheimer's.

"Among overweight people there were fewer deaths from those causes than expected," Flegal said in a telephone interview.

"There is some evidence that there might be something about nutritional reserves ... that makes you a better able to withstand an adverse situation," she said.

The study did find significant risks linked to obesity, including a higher risk of death from heart disease, Diabetes and kidney disease, and several cancers that have been linked with obesity, such as breast, colon and pancreatic cancer.

Flegal said the study was not intended to alter any public health recommendations. "Everybody should eat right, be active and not smoke," she said.

Dr. Louis Aronne, an obesity expert at New York-Presbyterian Hospital/Weill Cornell Medical Center, said it would be "dangerous as a society to assume it is OK to be overweight." (Editing by Maggie Fox;)